连续秸秆还田对黑土团聚体中有机碳含量及土壤肥力的影响

为了研究传统耕作方式下连续秸秆还田对黑土团聚体中有机碳分布及土壤肥力的影响，采用中国黑土区进行8年田间定位试验的大田土壤为研究对象，研究了无肥（CK）、单施化肥（NPK）和秸秆还田配施化肥（NPK＋S）3种处理对土壤水稳性团聚体中的有机碳含量及土壤养分的影响，并与2004年试验初期土壤进行比较。结果表明，与起始土壤相比，连续8年秸秆还田后，土壤大团聚体的含量显著提高，且NPK＋S处理下土壤大团聚体的含量及团聚体的平均重量直径（MWD）显著高于CK处理和NPK处理；连续秸秆还田8年后土壤的有机质（SOM）含量显著提高了6．59％，而CK处理和NPK处理均导致SOM含量下降，分别降低了1．95％和2．56％。与CK处理、NPK处理和起始土壤相比，NPK＋S处理提高了土壤各级团聚体内的有机碳含量，而且显著提高了大团聚体中有机碳对土壤有机碳的贡献率，降低了微团聚体中有机碳对土壤有机碳的贡献率；同时，秸秆还田配施化肥显著提高了土壤的碱解氮、有效磷和速效钾含量，其对土壤速效养分的改善程度要明显强于单施化肥处理。通过试验可以得出，秸秆还田配施化肥不仅能提高黑土团聚体的稳定性及其有机碳含量，还能明显改善土壤的养分状况，对黑土肥力提升具有积极意义。

Effects of Continuous Straw Returning on Organic Carbon Content in Aggregates and Fertility of Black Soil

In order to research the effect of continuous straw returning on soil fertility and organic carbon distribution in aggregates under the conventional tillage of black soil, soil samples were collected from an 8-year field experiment carried out in black soil region of China, the effects of different treatments (no fertilizer-CK, chemical fertilizers-NPK, and chemical fertilizers plus straw returning-NPK+S) on soil nutrients and organic carbon content in water-stable aggregates were studied, and the initial soil sample in 2004 was regarded as the comparison. Results showed that, the 8-year continuous straw returning significantly increased the proportion of macro-aggregates (>0.25 mm) as compared with initial soil. In addition, the amount of macro-aggregates and mean weight diameter (MWD) of aggregates in the NPK+S treatment were significantly higher than those in the CK and NPK treatments. Compared with the initial soil sample, the content of soil organic matter (SOM) increased by 6.59% under the NPK+S treatment, whereas under the CK and NPK treatments, it decreased by 1.95 and 2.56%, respectively. After 8-year straw returning, the organic carbon contents in soil aggregate had a general increase, obviously higher than these in the CK and NPK treatments. Contributing rates of SOC of macro-aggregates in soil organic carbon had remarkably increased after 8-year straw returning whereas it was contrary for the micro-aggregates. Meanwhile, chemical fertilizers plus straw returning significantly increased the contents of alkali-hydrolyzed N, available P and available K. Compared with NPK, NPK+S had a more remarkable improvement for the soil available nutrients. Consequently, the application of chemical fertilizer plus straw returning could be prone to increase the stability and organic carbon content of soil aggregates, as well as improve the soil nutrient condition, so it had profound significance on enhancing black soil quality comprehensively.